What Is Serotonin?

By Tess Thompson

Everything that we do, think or feel occurs due to the production, release and absorption of naturally occurring organic compounds known as neurochemicals, hormones or amino acids in the brain and body.

Imagine a sudden threat! The brain sends immediate signals to the concerned organ to take evasive action along with the release of certain neurotransmitters that activate production of hormones like adrenalin. Your alertness increases within a split second, eyes widen, the body becomes tense, the palms begin to sweat and the heart starts pounding. Similarly, mental stress, worry, mood swings and the overall state of mind is dependent upon the level of brain chemicals and hormones in the body.

Serotonin (5-hydroxytryptamine or 5-HT), is a neurotransmitter that is synthesized in the serotonergic neurons in the central nervous system. It is mainly involved in sleep, emotional responses like anger and aggression, depression and memory.

The neurons raphe nuclei (the part of the cell containing DNA and RNA) are the main source of production of serotonin. The raphe nuclei are neurons that are grouped in approximately nine pairs and spread throughout the length of the brainstem forming a network. Long nerve fibers that conduct away from the cell body of the neuron, called axons, from either side of neurons terminate in different parts of the brain as well as the spinal cord. This is known as the serotonin system. Serotonin is also present in the human gastrointestinal tract where it acts as a signal mediator.

Instead of the recognized neurotransmission from synaptic terminal buttons, scientists believe that serotonin is released from serotonergic swellings (varicosities) along axons. Once released, it spreads over a large region and activates the 5-HT receptors on the dendrites, the short fiber that conducts signals to neurons, cell bodies and nearby neurons.

Any substance or chemical that can produce, change or release serotonin is known as serotonergic. The action of serotonin can be inhibited by serotonergic agents, which are chemicals used in antidepressants like Selective Serotonin Reuptake Inhibitors (SSRI).

Apart from these sertonergic agents there are serotonin precursors like tryptophan, serotonergic enzymes, cofactors that are required for production of serotonin in the body.

The serotonergic system affects large areas of the brain, which is why SSRI drugs have the desired affect on mood and negative emotion. Low levels of serotonin have also been associated with suicidal tendencies. Research also reveals that serial killers normally consistently have low serotonin levels. A high level of serotonin produces a sense of emotional wellness but extremely high levels can be toxic and potentially fatal.

Genetics too plays an important role in the occurrence of psychological disorders and compromised emotional health. Abnormal serotonergic neurons in infants are one of the causes behind sudden infant death syndrome (SIDS).